what substrate on suspended bathroom floor ?

[sth]

hi - i have taken up old damaged floorboards (25mm thick) and want to put a ceramic tiled floor down - preferably to the same 25mm height as the old.
the joists are in good condition : 700mm wide and spaced 330mm apart.
is plywood the best option and what thickness would i need ? what are marmox boards - do they take the same weight ?
i have not bought tiles so don't yet know what thickness these will be...
i have time, so want to do a decent job - just don't have any expirience.
my fear is that water could get under the tiles and start rotting the wood beneath...

 

[brinkley]

thats what i said

 

[mikethetile]

take care against cold bridging at this point

you have room to allow a free circulation of air behind your stud. use a vapour barrier behind your boards

 

[peckers]

thats what i said

You got in just before me

 

[peckers]

take care against cold bridging at this point

you have room to allow a free circulation of air behind your stud. use a vapour barrier behind your boards

Thats what i was thinking

 

[sth]

thanks for the advice everyone. will sort floor first ...